Questions tagged [experiment-design]

The study of how to structure an information-gathering exercise where variation is present.

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experimental design in R project

I want to know of any repositories that contain complete experimental design in R covering basic tests and analyses? I want to take a top-bottom approach to learn step by step through a real project ...
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Correcting linear regression for change in air temperature over time

Say I collect temperature data over 5 square kilometers over the course of an hour in the evening but I want to analyze the data as though they were collected all at the same time. Naturally the area ...
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ANOVA and independent samples

Let's say there is an experiment of determining the best cookie recipe with 4 categorical factors. There are $S$ subjects that eat and rate cookies made using $R$ different recipes. There are $R$ ...
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Regarding the Plackett-Burman screening design

I am starting to implement screening designs in my optimization work. The one I am most familiar with is the Plackett-Burman design, so I am starting there. I have written my own scripts in MATLAB but ...
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Covariate for consistent estimation of treatment effect

I come across this sentence as I was reading journals: "to consistently estimate the treatment effect, any covariate X introduced must have equal expectations in treatment and control: E[X|Di= 1] =...
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Explanatory variables (exposures) that can be thought of as additive - best practices over multiple models?

I am modeling an exposure against an outcome (not COVID-19 related). The intended purpose of my analysis is to better understand (from a descriptive perspective) the nature of this exposure in regard ...
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Quasi-random sequence with discrete variables with differing number of levels

My question is probably worded incorrectly but here it is: I have (say) 3 discrete random variables: x1: has 15 levels (uniform pdf for simplicity) x2: has 3 levels (uniforms) x3: has 4 levels (...
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How many points for statistical significance in design of experiments

I am running an experiment that includes 27 input data points. The function yields results if we input $2 \leq x \leq 27$ points. I divide my data points in 9 sets of 3 points each. Now, I want to ...
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Should I pool samples or leave them separate before running a PERMANOVA?

I have a dataset of fish species from different sites within a harbour collected over 17 years. The dataset consists of 1,042 sampling transects collected at 6 specific locations where fish were ...
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How to deal with large combinations of factors

I am faced with a new problem that I cannot really tackle with the way I usually do my analyses and would appreciate any input you may have. The research goal is to identify the factors and ...
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analyze / model the difference between experiment and control group

In an experiment with experiment vs control groups, how to train model to explain the different results between experiment and control group (ie, has treatment vs no treatment)? Eg, customer ...
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Identifying the correlation between a slope and a level

Throughout this post, I assume at least second moments exist. Consider a heterogeneous linear treatment effect model of the form: $$Y_i = \alpha_i + \beta_i X_i$$ where $\alpha_i, \beta_i$ are ...
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Randomised or generalised block design?

sorry to ask a basic question, but I have not been super familiar with those types of experimental design yet and took over an already established experiment. Imagine those two set-ups: Three ...
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Ordinary least squares estimation explained in “Optimal Design of Experiments” by Goos/Jones, questions about some equationsEq

I am currently trying to become familiar with design of experiments with the book “Optimal design of experiments” by Goos and Jones. In chapter 2, they discuss the use of a Plackett–Burman type design ...
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How can I simulate an experiment and account for trial- and subject-level statistics?

I'd like to write some code to simulate a typical experiment but I have a bit of an issue and could use some feedback/ideas. My plan was to simulate a number of individual trials (each with a binary ...
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How can I evaluate the affect of risk scores on net revenue for an a/b test when there's some interaction from another test?

We conducted 2 separate A/B tests: the first has 3 variants - control, treat_a, treat_b where we modified a particular risk score in the hopes that we would increase net revenue. Coincidentally, there'...
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Which test should I use for a three alternative forced choice experiment?

I am running an online survey experiment where participants are randomly assigned to different treatment groups. They are asked to make a three alternative forced choice (3AFC) decision, i.e., pick A, ...
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Determine the variabilty of the volume given the length, width and height

I am to solve a problem where I am given the mean value, $\mu_i$ and variance, $\sigma^2_i$ where $i\in{L,W,H}$ which represents the Length, Widht and Height related variables respectively. The ...
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Power, split plot designs, and mixed models

My teammate and I are trying to determine the best way to allocated limited resources (shade cloth and fencing) in an experiment. We are considering 2 factors: light availability (2 levels) and water ...
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How to Test Significance of Trading Strategy? [closed]

I am wanting to try out a new trading strategy, and it has proven successful on a simulator for the past few days. I do want to collect some more data and see if my results are statistically ...
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gender effect measurement

An interesting study of gender effects in chess showed that when women played men without knowing that they were playing men, they performed better than when knowing they were playing men. I was ...
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Is a GLMM applicable in a non-full factorial experimental design with two dependent fixed effects?

At the moment I plan the statistics for an upcoming experiment in Biology with two fixed effects whose effect on a fitness parameter of a parasite I would like to test. The two fixed effects are the ...
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Insufficient power from pwr.p.test

Using the pwr package, I determined the optimal sample size of 38. However, when I ran simulations using this sample size, I only get a power of 70%. What's going ...
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strange ordinal regression - does it exist, what is it called, how do I do it properly

My daughter is making cookies for her science project. She is trying to "use statistics to optimize the recipe". She has asked for my help in the science part. Currently: She wants the ...
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Question about Within Subjects V.S. Between Subjects

What are two advantages and two disadvantages of within-subjects designs (designs with repeated measures) in comparison with between-subjects designs?
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Experimental Design for count data in a (4X2) Factorial with replication

I am in need of help choosing a statistical model for count data with experimental replication. The Experiment (4 X 2 Factorial experimental design) -Factor A = Control, Low, Medium, High. -Factor B = ...
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Sample Inclusion Criteria for an Intent-To-Treat Analysis in an Encouragement Design With One-Sided Non-Compliance

This question is about how to define the sample in an Intent-To-Treat analysis of an experiment with balanced pre-assignment and an encouragement design. This is a bit different than the usual setting ...
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Split-Split-Split Plot Design

I have an experiment which was set up as a split-split-split plot design and repeated the experiment a second year. 2yrs x 4 reps x 2 levels of Factor A X 5 Levels, of factor B X 2 Levels, of Factor C ...
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Analyzing a counterfactual in observational studies?

In observational studies, when randomization is not an option (everyone is treated), it is necessary to estimate a counterfactual of what would have happened in the absence of treatment. Once you ...
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How do you analyze an unbalanced fractional factorial design?

I'm interested in learning about unbalanced fractional factorial designs. If they are possible to analyze, what are the drawbacks to using them? Just usual loss of orthogonality? How does analyzing ...
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Confidence interval of Relative Change using Delta method

I have the following equation for relative change (RC): RC = (P1 - P2)/P2 * 100 Here, P1 and P2 are both ratios. For example, P1 = A1/n1 and P2 = A2/n2, where n1 and n2 are the sample sizes of both P1 ...
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Remove points, but preserve diversity

Given a finite set of points in $\mathbb{R}^n$, all at finite distances from each other I would like to remove a certain proportion of points, in such a way as to penalise clustering. For example for $...
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How should I test for the effect of an interaction with “uneven” levels?

Basic Effect Is there a difference between the conditions of "Factor A"? That is, A1 vs. A21. In A1 participants see a paragraph of text. A2 is a combination of A1 + another paragraph of ...
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Questions about Data Analysis

For my research I'm examining whether applying a certain promotional intervention improves the amount of misshapen products bought. The study contains of two parts. In part 1 Scanner data from ...
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Question regarding Optimal Designs of experiments

I'm a bit unclear on the concept of optimal design of a data matrix $X$. I propose a small example to work through: Suppose $\epsilon_i \sim N(0, \sigma^2)$ are i.i.d., and I have some experiment ...
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Competition with randomized teams that eventually teases out best individual performers

I seek to set-up a competitive league among friends. ~8 individuals total. ~50 total 2-on-2 matches (2 matches played simultaneously per round). Pairings shuffled after each round. Goal: individual ...
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D-optimal design with nuisance parameters

I am a mechanical engineer trying to develope an optimal design of experiments in a problem with nuisance parameters. I would like to calculate the parameters $\mathbf{d}$ to optimally estimate ...
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Number of Tests necessary for object detection (test/experiment design)

I want to find out the number of tests necessary to validate certain performance characteristics of an object detection system with a certain confidence. The system just detects if a relevant object ...
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Testing for differences between pooled biological samples

I am trying to test for differences in absorbance between a control and treatment group. Due to cost, each measurement is derived from the mixture of 5 independent samples. Overall there are 5 ...
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How to estimate this effect?

I have data with columns like this: [individual, song, is_after_drinking (IAD), enjoyment] I have observations on an indivudal J rating a song K (n=800 ...
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Statistically, is it effective to design exams to get harder as you answer correctly?

I think we have all taken exams where as you answer more questions correctly, the exam gets harder. Intuitively, this is obvious why...If an IQ test had questions for 3rd graders, everyone would get ...
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Treating site and year as an integrated factor

I’m analyzing an experiment where we collected data across 4 different treatments. These treatments were replicated over two years. In each year, we set-up the experiment at 2 different sites. In ...
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How to test if term is correlated to news category

Suppose we have a corpus of news articles that contain a term. We also have the category for each article, which ranges from Sports to Politics, etc. What statistical approach would we take to ...
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A difference in difference experiment with multiple interventions

Say you have a control group and an experimental group and you have verified the parallel trends assumption for them. Now say that at the time of intervention, the control group gets 9 separate ...
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Is peeking in A/B tests bad even if you don't stop your experiment?

I have been asked a test about A/B testing that I'm unsure how to answer. Say you're running a conversion rate experiment, and my A variation has a conversion rate of 2% and my B variation has a 2.2% ...
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A theoretical question on fractional factorials

Very much in need of help interpreting this if anyone is available.. Thank you! Fractional factorials that include many factors can sometimes have a surprisingly low number of experimental conditions ...
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Analyzing clustered (repeated measures) data with very few clusters

What is the most appropriate method for analyzing clustered data (i.e., repeated measurements nested within subjects) when there are very few clusters (e.g., 3 subjects)? Here's a brief description of ...
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How to build a GLMM that observes the years since experimental design was established?

Hello, my first question, quite individual, so I find it difficult to relate already answered questions to mine. I have observed the vegetation development in forests of 5 different areas (...
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How to best respond to investigator who wants to study secondary outcome

I'm co-investigator on a clinical trial where the we are studying the effect of an intervention. The study is powered to detect a clinically meaningful change for some primary endpoint. My questions ...
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Appropriate statistical test to use

I am running an experiment where I am testing the difference in effectiveness of constructed wetlands. Essentially, I have a control with unplanted wetlands and treatment with planted wetlands and its ...

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